This portable is 3 years old. Some months ago it started freezing on startup. Shut down and restart and it would be OK. Finally it would not pass a flashing cursor on start up and I had the local PC support chap look at it. He's diagnosed many things, from overheating (dust removed from casing), hdd (problem continued with new hdd so original returned to computer), corruption in the startup sector of OS (Vista Home Premium). Unable to locate a version of Vista, he installed Windows7 Enterprise which has now worked for some weeks. I guess he also changed the BIOS as the BIOS options and font changed at this time. It worked well until yesterday. It now hangs at the "starting windows" screen and logo.
Yesterday he diagnosed an unstable memory chip which he has removed and the computer worked for a few hours. On shut down I allowed a Windows update to install and left it to it. When I returned the laptop had entered power save mode and frozen with a black screen. It will not go beyond the starting windows logo and the recovery option just produces a black screen. Ideas anyone?